A skill that takes a year to learn is also secretly teaching you how to wait.
STILLNESS
STILLNESS
Long projects train two things at once. There is the skill itself, and underneath it the capacity to keep going through the middle stretch where improvement is invisible and nothing is rewarding. That second thing transfers to everything else you will ever attempt, and it can only be built by actually waiting through something.
Choose one thing with a long horizon and commit to it in months rather than sessions. Keep a record of where you started so the slow progress stays visible to you. When it gets dull, notice that the dullness is part of the training rather than a sign you picked wrong.
What skill have you quit because the payoff sat too far off?
Free, with nothing to buy inside it.